Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, video and the like, and deployments are likely to increase with introduction of new data oriented systems such as Long Term Evolution (LTE) systems. Wireless communications systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, LTE systems and other orthogonal frequency division multiple access (OFDMA) systems.
An orthogonal frequency division multiplex (OFDM) communication system effectively partitions the overall system bandwidth into multiple (NF) subcarriers, which may also be referred to as frequency sub-channels, tones, or frequency bins. For an OFDM system, the data to be transmitted (i.e., the information bits) is first encoded with a particular coding scheme to generate coded bits, and the coded bits are further grouped into multi-bit symbols that are then mapped to modulation symbols. Each modulation symbol corresponds to a point in a signal constellation defined by a particular modulation scheme (e.g., M-PSK or M-QAM) used for data transmission. At each time interval that may be dependent on the bandwidth of each frequency subcarrier, a modulation symbol may be transmitted on each of the NF frequency subcarrier. Thus, OFDM may be used to combat inter-symbol interference caused by frequency selective fading, which is characterized by different amounts of attenuation across the system bandwidth.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals (also referred to as user equipments (UEs) or access terminals (ATs)). Each terminal communicates with one or more base stations (also referred to as access points (APs)) via transmissions on forward and reverse links. The forward link (also referred to as a downlink) refers to the communication link from the base stations to the terminals, and the reverse link (also referred to as an uplink) refers to the communication link from the terminals to the base stations. These communication links may be established via a single-in-single-out (SISO), single-in-multiple-out (SIMO), multiple-in-single-out (MISO) or a multiple-in-multiple-out (MIMO) system.
As the number of devices increases, the need for proper bandwidth utilization for data and control signaling on licensed as well as unlicensed or shared spectrum becomes more important. Moreover, with the introduction of semiautonomous base stations (e.g., femtonodes and piconodes) for managing small cells, such as femtocells and picocells, in systems such as LTE, avoiding interference with existing base stations, as well as allocation and management of various channels, such as unlicensed or shared channels, which may be white space channels, authorized shared multiuser (ASM) channels, instrumentation scientific and measurement (ISM) channels, or other shared channels may become increasingly important.